Mr. Paul, in an interview, said convention planners had offered him an opportunity to speak under two conditions: that he deliver remarks vetted by the Romney campaign, and that he give a full-fledged endorsement of Mr. Romney. He declined.

“It wouldn’t be my speech,” Mr. Paul said. “That would undo everything I’ve done in the last 30 years. I don’t fully endorse him for president.”

Mr. Paul’s campaign chairman, Jesse Benton, acknowledged the frustrations that the Paul high command had been forced to manage.